LifeP04 4 to 8 cell

[Norm01]

I have four CATL 302Ah with a Daly BMS, everything is working great. I have the room to add 4 more cells, do I just get a second 4s BMS and plug them in parallel or is there a way to run them is series at 24v and have a 8s BMS that would output 12v and accept a 12v charge. This is for an RV and my 3 chargers are 12v and obviously I need a 12v output.

 

[TacomaJoe]

You can't get 12V from an 8s BMS. Best bet is to make another 4s battery with BMS and parallel it into the RV.

 

[meetyg]

Or you could parallel two cells, to make 4s2p with the existing BMS.
But the advantage of have another 4s pack with its own BMS is that you double up the charge/discharge ampacity, and it gives you redundancy. But, please make sure to fully charge both pack before connecting in parallel. This will prevent problems like a large inrush current when paralleling.

 

[Norm01]

So two 4S1P batteries in parallel to make a 4S2P battery seems suitable. My inverter is 2000w so two 100A BMS would do. Is active balancing needed or a good idea. What would you guys recommend for 2 BMS @ 100a each to put in parallel

 

[Rocketman]

Use the same bms’s on both batteries. Just make sure you can read individual cell voltages (most can now days). That way you can know if the two batteries are getting out of sync.

If your happy with your current bms - just get another.

Be careful when hooking the two batteries up - so you don’t have uneven charging and draws -

Good Luck

 

[TimE]

So two 4S1P batteries in parallel to make a 4S2P battery seems suitable. My inverter is 2000w so two 100A BMS would do. Is active balancing needed or a good idea. What would you guys recommend for 2 BMS @ 100a each to put in parallel

Get a pair of JK 200A bms. Run the batteries in parallel and you will be able to run high loads off your batteries if you need to.

 

[Steve_S]

I agree with TimE, built two 12V batteries with 200A or even 250A BMS as the cells can certainly deal with it and have lots of available power if needed. Room to upgrade inverter if you need/want. 12V@250A will give you 3000W +surge.

 

[Norm01]

Just ordered 2 JK 200A with heat control. I’ll build two separate batteries for redundancy and hook them up in parallel.

 

[Norm01]

BMS are JK-B1A8S20P-H-C, found a manual which is basically junk. The power wires are dual connections so for 200A I’m getting 2 x 4AWG. Is that right.